1. Field of the Invention
This invention relates to an image forming apparatus using an electrophographic method and, more particularly, to an image forming apparatus precisely detecting a consumption amount of toners.
2. Description of Related Art
In electrophotographic recording apparatuses such as electrophotographic printers, after a surface of a photosensitive drum is negatively charged uniformly with a charging roller, electrostatic latent images are written over the surface with an LED (light emitting device) head. Toner images are formed to the electrostatic latent images using such as developing rollers and toner conveying rollers. The toner image is transferred to a recording medium with a transfer device. The transferred toner is fixed to the recording medium using a fixing device. A part of toner remaining on the surface of the photosensitive drum after the fixing step is carried to the developing roller as remaining on the surface of the photosensitive drum and is collected by the developing roller. The collected toner is reused as mixed with the toner stored in the developing device. Images are reproduced as the above processes are successively repeated. As an example of such an electrophotographic printer, an apparatus has been known in which a voltage supplied to the developing roller is adjusted according to a degree of impairment in device's specification (see, e.g., Japanese Patent Application Publication (JA) No. 2004-233,436).
With such a conventional electrophotographic system, as described above, the toner consumption amount is detected by counting up printing dots of image data to be printed. For example, where the sizes of the printing dots are changed at each printing dot by making the exposure amounts (or light emitting amounts) from the LED head different from one another, however, some deviations may occur between the toner consumption amount calculated by counting up the printing dots and the actual toner consumption amount, so that there raises a problem such that a precise toner consumption amount cannot be obtained.
It is an object of the invention to provide an image forming apparatus capable of calculating a toner consumption amount.